And just checked, same issue with my Show Desktop key, which I reconfigured from Ctrl-Alt-D to Super-D.
$ xfconf-query -c xfce4-keyboard-shortcuts -lv | grep desktop /xfwm4/custom/<Primary><Alt>d show_desktop_key /xfwm4/custom/<Super>d show_desktop_key /xfwm4/default/<Control><Alt>d show_desktop_key /xfwm4/default/<Primary><Alt>d show_desktop_key
And just checked, same issue with my Show Desktop key, which I reconfigured from Ctrl-Alt-D to Super-D.
$ xfconf-query -c xfce4-keyboard- shortcuts -lv | grep desktop custom/ <Primary> <Alt>d show_desktop_key custom/ <Super> d show_desktop_key default/ <Control> <Alt>d show_desktop_key default/ <Primary> <Alt>d show_desktop_key
/xfwm4/
/xfwm4/
/xfwm4/
/xfwm4/